Method of shaping hollow metal articles



Jan. 28, 1958 J. A. RZEZUTKO ETAL 2,821,012

METHOD OF SHAPING HOLLOW METAL ARTICLES Filed March 3, 1955 United States Patent METHOD OF SHAPING HOLLOW lVlETAL ARTICLES qsell A- R zu k troi and an C- l H aa P a ish-rass en to A ge an Me a o ucts Company, Detroit, Mich, a corporation of Mi h an Application Mar-c113, 1955, Serial-No. 491,814 4 Claims. (Cl. 29- -1563) This invention relates to blades for turbines, compressors and the like, and particularly to a method of forming the blade to a desired cross-sectional shape after it is assembled;

The blade Ofthe present-invention is made from a casting having an arcuate wall with a longitudinal rib intermediate the ends and a pair of 'trunnions on the end walls. A thin sheet of material is secured to the casting in engagement with-the rib and brazed thereto, leaving a hollow interior on eachside of the rib. One of the hubs has an aperture therethrough communicating with the interior on one side of the rib. An aperture is provided in the sheet of material located adjacent to the end having the hub, with the aperture communicating with the hollow interior on the opposite side of the rib. The rib has an aperture provided therethrough adjacent to the end opposite to that having the apertures in the hub and sheet. With this arrangement, air can be blown into the interior through the hub, which passes lengthwise through the blade on one side of the rib, through the aperture at the end thereof, and returned through the interior on the opposite side of the rib and out through the aperture in the sheet.

Difiiculty was experienced in shaping the blade to an exact cross-sectional contour while maintaining a desired form longitudinally of the blade. This difiiculty has been overcome by the present invention which embodies the striking of the assembled blade in a die after it has the sheet applied thereto and dressed to approximate form.

The hollow interior of the blade is filled with water and frozen to form ice, after which the blade is placed in a die and pressure applied, which permits the blade to be shaped to conform to the die cavity. When pressure on the die set is applied in an area of the blade, the ice will be melted to a slight degree so that the metal can be formed to the shape of the cavity. After the blade has been so formed, it is then placed in a rack so that the ice may melt and the water drain from the blade, thereby eliminating any foreign matter which otherwise would remain within the hollow interior. The use of the ice is unique in that it is extremely hard and at the same time, in areas where the pressure is applied, it will melt sufliciently to flow to permit the metal to be shaped to the cavity.

Accordingly, the main objects of the invention are: to form hollow blades to a desired contour in a die set after the interior is filled with water and frozen; to fill the blades with water and cool the blade and water to form ice to prevent the collapse of the walls of the blade when formed to a desired shape in the cavity of a die set, and, in general, to provide a method for shaping hollow blades to a predetermined contour which is simple and economical in practice.

Other subjects and features of novelty of the invention will be specifically pointed out or will become apparent when referring, for a better understanding of the in- "ice vention, to the following description taken in conjunction with the accompanying drawing, wherein:

Figure 1 is a broken perspective view of a blade which is shaped to desired cross section and form by the method of the present invention;

Fig. 2 is a sectional view of the structure illustrated in Fig. 1, taken on the line 2-2 thereof;

Fig. 3 is a sectional view of the blade illustrated in Fig. 1, taken on the line 33 thereof, and

Fig. 4 is a sectional view of the die set and blade after the forming operation.

The blade of the present invention comprises a casting 10 having a body 11 of transverse arcuate shape terminating in end wall portions 12 and 13 from which trunnions 14 and 15 extend. Each of the trunnions is provided with a washerlike shoulder 16. A rib 17 extends longitudinally of the body 11 from the end wall 13 approximately to the end Wall 12, being spaced therefrom to provide an aperture 18. A formed sheet of material 19, also of arcuate shape, has the forward end '21 reversely bent in position to engage ashouldered edge portion 22 of the body 11. The reversely bent portion 21 is brazed or otherwise secured to the shouldered portion 22 and the rear edge 23 is similarly secured to the rear edge of the body 11'. The ends and medial portion of the sheet are brazed or otherwise secured to the end walls 12 and 13 and the rib 17. The blade so constructed is then dressed to approximate form ready to be shaped to the exact cross-sectional contour and longitudinal form.

The trunnion 15 and adjacent wall 13 have an aperture 24 extending therethrough communicating with the hollow interior 25 forward of the rib 17. An aperture 26 is provided in the face of the sheet 19 adjacent to the end wall 13 communicating with the hollow interior 27 rearwardly of the rib 17. The two hollow interiors 25 and 27 communicate with each other through the aperture 18 adjacent to the trunnion 14. The hollow interiors permit a flow of air through the blade to keep it cool during operation, but provide no rigidity to permit the blade to be shaped during the forming operation.

To provide the required rigidity for forming the contour, the blade is filled with water in a manner to permit the air to escape during the filling operation. After the aperture 26 is closed by adhesive tape and the entire interior area is filled with water, the aperture 24 in the trunnion 15 is plugged and the blade and water are reduced in temperature beyond a point where ice is formed from the water in the hollow interior of the blade. The adhesive tape is removed from the aperture 26 and the blade is then placed in a cavity 31 of a die set composed of an upper die element 28 and a lower die element 29. Thereafter, the die elements are moved together under substantial pressure, forcing the blade to assume the contour of the cavity. A maximum pressure will be applied at points requiring forming, whereat a film of water will melt from the ice due to the pressure which will shift within the hollow interior as the body 11 and sheet 19 are shaped to the cavity. The ice within the hollow interior prevents the collapse of the body and sheet so that they can be shaped to the form of the cavity as the pressure melts the ice to permit the forming operation. The blade is then removed from the die set, the plug removed from the aperture 24 in the trunnion 15, and the unit is permitted to warm in the ambient air so that the ice will eventually melt and fiow from the apertures 24 and 26. The ice formed within the hollow interior of the blade provides a desired rigidity, preventing the collapse of either the body 11 or sheet 19 during the die forming operation. After the operation, the water from the melted ice is free to fiow from the blade, eliminating an operation of cleaning the interior of the blade 7 of foreign matter.

What is claimed is:

1. The method of shaping a hollow blade to a desired form which includes the steps of: filling the interior with water, freezing the water to ice, placing the blade within the cavity of a die set, applyingpressure to the die set to shape the blade to the cavity, and thereafter melting the ice and permitting the water to drain from the blade.

2. The method of shaping a hollow blade having a divided interior communicating with a pair of apertures at one end thereof which includes the steps of: filling the divided hollow interior with water, closing the pair of apertures to retain the waterrthe'rein, freezing the blade so as to form ice within the divided interior, and shaping the blade within the cavity of a die set to a desired contour.

3. The method of constructing a blade having a hollow interior through which air may be blown to prevent the blade from being overheated which includes the steps of: casting a body portion to provide a thin arcuate wall having a thin central rib, two end walls and trunnions ,on the end walls, securing a sheet of material to the rib,

the two edges and end walls of the cast body, thereby forming a U-shaped passageway the adjacent ends of which communicate with the atmosphere through an aperture in the trunnion and in the sheet, filling the U-shaped passageway with water, closing the apertures to retain the water within the passageway, freezing the Water to form ice which prevents the walls of the blade from collapsing, and shaping said walls to a desired contour within the cavity of a die set to which pressure is applied,

4. The method of shaping a hollow blade which has a passageway on one side of a rib communicating with an aperture in an end trunnion and with a passageway on the opposite side of the rib which communicates with an aperture through the wall of the blade adjacent to said hollow trunnion which includes the steps of: filling the passageways with water, closing the aperturein the wall and in the trunnion to retain the water therein, 10wering the temperature of the blade sufliciently to freeze the water to form ice which prevents the collapse of the wall when being shaped, in a die set, and shaping said blade within the cavity of a die set under suflicient pressure to cause said ice to melt at the points of applied pressure so that the walls of the blade may'conform to the shape of the cavity.

References Cited in the file of this patent UNITED STATES PATENTS 2,205,132 Blanchard June 18, 1940 2,359,466 Currie Oct. 3, 1944 2,458,189 Morgan Jan. 4, 1949 2,522,100 Diller Sept. 12,1950 

